Quality assessment of three species of commercially produced Trichogramma and the first report of thelytoky in commercially produced Trichogramma

Weekly shipments of Trichogramma pretiosum Riley, Trichogramma minutum Riley, and Trichogramma brassicae (Bezdenko) (Hymenoptera: Trichogrammatidae) from a single insectary were assessed to determine whether survivorship with and without honey, emergence rate, and sex ratio were consistent over a five-week period in 2000. At least one shipment was misidentified by the insectary. Emergence rates were over 75% in 15 out of 17 shipments, although emergence varied significantly over the experimental period for each species. Mean longevity of honey-fed individuals was 7.16 days for T. pretiosum, 6.71 days for T. minutum, and 4.02 days for T. brassicae; mean longevity of unfed individuals was 2.68 days, 2.42 days, and 1.96 days, respectively. Mean sex ratios (proportion of individuals that were male) were 0.029 for T. pretiosum, 0.465 for T. minutum, and 0.444 for T. brassicae. Seventeen out of 18 virgin T. pretiosum females produced daughters, and three out of a subset of six of these females produced sons after being fed the antibiotic tetracycline. These results are consistent with infection by a parthenogenesis-inducing strain of Wolbachia.